Re: [Int-area] New Version Notification for draft-bonica-intarea-lossless-pmtud-00.txt

[Manoj Nayak <[e-mail]>]

Hello Joe,

Please find my reply.

>>- why does this doc assume the max ICMP is 576?
>>       we?re still talking IPv4 here; it?s still 68 (that?s why only 64 bits of the orig payload are guaranteed)
>>       (yes, your note in the end of sec 1 is relevant, but given v4-in-v4 tunneling, it?s possible that 
>> paths might be smaller than the 576 assumption)
 
We use an unused field in first 8 bytes of ICMP error/reply message. How the idea would be
affected if minimum packet size is 68 bytes or 576 bytes. As per my understanding,
existing ICMP error/reply message works in v4-in-v4 tunnelling, so it would continue to 
work with the idea proposed in our draft. we won’t let the ICMP message exceed a reasonable size. 
in our implementation, that will be 576.
 
 

>>- why would this approach find the largest fragment through a system?
>>       rfc1812 talks about various strategies, one of which is ?equal sized?, which might never find 
>> the max the way you propose
 

As per section 4.2.2.7 from rfc 1812,
 
“There are several fragmentation techniques in common use in the
Internet.  One involves splitting the IP datagram into IP
fragments with the first being MTU sized, and the others being
approximately the same size, smaller than the MTU. “
 
In both of the above cases, idea in our draft works. In our implementation,
We can assume the first fragment to be largest fragment. This first fragment remains
Largest fragment unless until one more fragment is found to be greater than the first fragment.
 
For example:
 
While assembling the fragments, 
 
   I=0;
   Largest Fragment = packet-I;
   For (, I < n , ++I)
      If ( packet-I > Largest Fragment)
        Largest Fragment = packet-I;
 
Hopefully I did not miss anything.

Regards
Manoj Nayak
    
    ------------------------------
    
    Message: 3
    Date: Tue, 29 Oct 2019 21:43:33 -0700
    From: Joe Touch <[e-mail]>
    To: Ron Bonica <rbonica=[e-mail]>
    Cc: "[e-mail]" <[e-mail]>
    Subject: Re: [Int-area] New Version Notification for
    	draft-bonica-intarea-lossless-pmtud-00.txt
    Message-ID: <[e-mail]>
    Content-Type: text/plain;	charset=utf-8
    
    Hi, Ron,
    
    A few things come to mind. The first one, IMO, renders the rest somewhat less important.
    
    Joe
    
    -------------
    
    - this approach applies only to IPv4; not sure it?s worth trying to optimize for only that case
    	(it requires on-path fragmentation permitted)
    
    - this approach relies on ICMPs, so it?s as robust (or, more to the point, not) as PMTUD
    	if ICMPs can find the reverse path from the dest, why wouldn?t the routers?
    	i.e., isn?t the problem with ICMPs not just routers not sending them but firewalls BLOCKING them?
    	(i.e., if ICMPs would work here, PMTU would have worked, rendering this unnecessary)
    
    - why does this doc assume the max ICMP is 576?
    	we?re still talking IPv4 here; it?s still 68 (that?s why only 64 bits of the orig payload are guaranteed)
    	(yes, your note in the end of sec 1 is relevant, but given v4-in-v4 tunneling, it?s possible that paths might be smaller than the 576 assumption)
    
    - why would this approach find the largest fragment through a system?
    	rfc1812 talks about various strategies, one of which is ?equal sized?, which might never find the max the way you propose 
    
    
    > On Oct 29, 2019, at 9:53 AM, Ron Bonica <rbonica=[e-mail]> wrote:
    > 
    > Folks,
    > 
    > Please review and comment.
    > 
    >                        Ron
    > 
    > 
    > 
    > Juniper Business Use Only
    > 
    > -----Original Message-----
    > From: [e-mail] <[e-mail]> 
    > Sent: Tuesday, October 29, 2019 11:48 AM
    > To: Ron Bonica <[e-mail]>; Hakan Alpan <[e-mail]>; Radon Rosborough <[e-mail]>; Bradely Newton <[e-mail]>; Miles President <[e-mail]>; Manoj Nayak <[e-mail]>
    > Subject: New Version Notification for draft-bonica-intarea-lossless-pmtud-00.txt
    > 
    > 
    > A new version of I-D, draft-bonica-intarea-lossless-pmtud-00.txt
    > has been successfully submitted by Ron Bonica and posted to the IETF repository.
    > 
    > Name:		draft-bonica-intarea-lossless-pmtud
    > Revision:	00
    > Title:		Lossless Path MTU Discovery (PMTUD)
    > Document date:	2019-10-29
    > Group:		Individual Submission
    > Pages:		8
    > URL:            https://urldefense.com/v3/__https://tools.ietf.org/html/draft-bonica-intarea-lossless-pmtud-00__;!8WoA6RjC81c!XifH7EcqHRKXHyGSwB3ojXm6YmKn_vYWCjgM-VDTPTEzP-khJGlb9MqM8x-YTELKJ64$ 
    > 
    > 
    > 
    > Abstract:
    >   This document describes alternative IPv4 PMTUD procedures that do not
    >   prevent IP fragmentation and do no rely on the network's ability to
    >   deliver ICMP Destination Unreachable messages to the source node.
    >   This document also defines a new ICMP message.  IPv4 nodes emit this
    >   new message when they reassemble a fragmented packet.
    > 
    > 
    > 
    > 
    > Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org.
    > 
    > The IETF Secretariat
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